190 WET FOREST COMMUNITIES 



thickness of the shrubs prevents the growth of herbaceous vegetation. 

 The shrub stratum is the chief habitat. 



The buttonbush is remarkably free from plant-feeding animals. 

 Occasionally some of the willow-eaters, such as the larva of the smeared 

 dagger-moth, are found on it, but never in any numbers. This stratum 

 is the resting-place of many of the insects whose early stages inhabit 

 water. When the plants are in blossom, it is visited by many flower- 

 frequenting insects, such as the bumblebee (40). 



Mr. Visher has recorded a number of nesting birds in this girdle. 

 The wood-duck usually makes its nest here in some hollow tree and lines 

 it with feathers; where stumps or rotten trunks are found the prothono- 

 tary warbler sometimes nests; Traill's flycatcher (Empidonax trailli 

 Aud.) places its nest well up in the branches and leaves of the bushes. 



c) Forest formation (Stations 52 and 53; Table L). — As time goes 

 on and the marsh fills with organic detritus, the buttonbush which is 

 continually encroaching upon it comes to occupy a position farther in, 

 while its former location is taken by the ash, which is the next girdle 

 outside. 



The ash is succeeded by the American elm and the basswood. These 

 are frequently considerably mixed with the ash, but the two girdles can 

 be distinguished in the Wolf Lake Forest. For convenience we shall 

 treat these two girdles (associations) together under the head of the wet 

 forest formation. 



The subaqueous and subterranean-ground strata: The subterranean 

 portion is inhabited by earthworms. On the higher parts there are 

 doubtless other subterranean forms. Where the roots of the grapevine 

 are in the drier soil, the vines are infested with the aphid (Phylloxera) 

 which makes galls on both roots and leaves. The depressions of these 

 forests are filled with water in spring and support temporary pond ani- 

 mals such as we have discussed on p. 179. 



In the Wolf Lake woods we noted in the spring of 19 10 that the small 

 red spiders (Trombidium sp.) were numerous. Centipedes, crane-fly 

 larvae, and ground beetles occur under the leaves. Hancock (40, p. 419) 

 states that the obscure and Indiana grouse locusts [Tettix obscura Han. 

 and Neotettix hancocki Bl.) are found in such forests. Under pieces of 

 rotten wood are sometimes found specimens of the small snail (Zonitoides 

 arbor eus), which is first to appear in forests developing from the button- 

 bush swamp stages. On highest ground we get two other snails (Poly- 

 gyra monodon and Pyramidula striatella Ant.) (91, 100). In the fallen 

 logs we find a considerable number of borers (Parandra brunnea Fabr. 



